Lubricating of leather



Patented Apr. 26, 1938 UNITED STATES LUBRICATING OF LEATHER Alphons 0. Jaeger, Mount Lebanon, Pa... minor to American Cyanamid & Chemical Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application August 8, 1938,

Serial No. 95,031

31 Claim.

This invention relates to .the tat-liquoring,

stufiing and oiling of hides, skins and leather for the purpose of lubricating the fibers oi the same,

and to the filling of sole leather, and deals primarily with new classes of materials for use in theseprocesses. An object of the invention is to provide a new lubricated leather or skin which will be more resistant to light and oxidation and of more uniform quality than those finished by processes at present in use. A second object o! the invention is the provision of new classes of materials for accomplishing the above purpose,

which materials can be manufactured in uniform quality from relatively inexpensive raw materials and will not be subject to great fluctuations. in market price.

be apparent from the following description, when taken with the appended claims.

The application of oils, greases and other materials having lubricating properties to skins and leather takes place in a number of the steps ordinarily practiced in the production of leather of varying grades. An important example is the process known as fat-liquoring, in which the hides after vegetable or mineral tannage are treated with an aqueous emulsion of an oil or fat to lubricate the fibers of the leather. This step, for instance, is used in finishing all upper leather, glove leather and other light grades of 3o leather. Another example is the step known as stufllng, in which the leather is treated with oils or greases in the absence of substantial amounts of water in order to lubricate the fibers thereof. Another example is the process known as oiling of 5 heavy leather in which animal, vegetable and mineral oils are drummed or otherwise introduced into the properly pre-treated leather and are relied upon as the lubricating agents.

The materials most commonly used in oiling, stufiing and fat-liquoring of leather are stated in Wilson The Chemistry of Leather Manufacture to be glycerides of the animal or vegetable oil type such as olive oil, linseed oil, cod liver oil, coconut oil, menhaden oil, neats-foot oil, moellon degras, also hydrocarbon oils, etc. as well as free fatty acids such as the fatty acids of linseed oil, fatty acids of cod liver oil, etc. For use in stuifing and fat-liquoring, Wilson lists eight general classes of materials, namely, (1) true oils and fats; (2) soaps made from these oils and fats;- (3) sulfonation products of these oils and fats; (4) waxes; (5) resins; (6) hydrocarbons; ('7) moellon degras; and (8) eggyolk. Under the.

heading of resins, colophony is the only substance 56 specifically described, this being ordinarily tur- Further objects will pentine rosin and consisting mostly of the anhydride of ,abietic acid. It will be noted that all these materials are natural substances or sulionation products thereof, and that the physical characteristics and suitability of any one 01 them will be subject to variation in accordance with its degree of purity. Even with these limitations, however, natural products of this type have been the only oils employed by the tanner, throughout the many centuries during which leather has 10 been tanned and finished.

I have now made the surprising discovery that a class of substances which has hitherto been used for an. entirely unrelated purpose may be transferred bodily into thefield of oiling, stuffing and tat-liquoring of leather, and that the characteristics of this class or materials are such that every member thereof can be used to advantage ior this purpose. These are the socalled plasticizers and solvent softeners which 20 are at present used in large quantities in the manufacture of paints, varnishes, lacquers and synthetic resins, and which have reached a high state of development for these purposes. Briefly, these plasticizers and solvent softeners are rela- 25 tively water insoluble, organic compounds having relatively low softening points, relatively low vapor pressures, and great chemical stability and resistance to decomposition. Many of these compounds have such low vapor pressures that they cannot be distilled without decomposition under any vacuum.

Most of these plasticizers and softeners belong chemically to the class 01' high boiling esters of organic acids, practically all of the remainder be- 5 mg esters of inorganic acids such as phosphoric or amines, amides, sulfonamides and similar substances. The above classification includes all those organic substances having known plasticizing and softening properties on synthetic resins, lacquers, paints and varnishes, but by far the greatest quantity or synthetic plasticizers in commercial use today are esters of organic acids such as dlmethyl, diethyl and dibutyl phthalates. It should be noted that some of the natural oils and fats which are listed above have also been used, in unoxidized or oxidized form, in the field of paints, varnishes, lacquers and synthetic resins. These substances, however, are not plasticizers within the meaning of the term as it is used in in the present specification. Accordingly, the term "non-oleaginous plasticizer will be used in the specification and claims to define broadly the synthetic plasticizers of the present invention, which are synthetic materials having aplasticizing action and containing radicals not present in natural oils and. fats. The term "non-oleaginous ester" will be used in defining some of the more limited aspects of the invention, and it is understood that both terms are used to exclude the natural oils and fats, rather than as a limitation on the physical characteristics of the plasticizers and esters to which they refer.

In the field for which the plasticizers and softeners were originally developed, they served to impart plasticity and greater flexibility to the resinous compositions and films with which they were associated. I have now found that these same characteristics are imparted by the plasticizers to hides, skins and leather when they are incorporated therein, and that the largest class of plasticizers, namely, the low vapor pressure esters of organic acids, will also serve the important function of lubricating the fibers of the skins or leather to such an extent that the use of additional lubricants of the type previously discussed may be dispensed with if desired. In fact, I have found that many of these low vapor pressure esters have such excellent lubricating properties for skins and leather that in some cases they may be used in much smaller amounts than was previously considered necessary with the lubricating agents formerly employed.

A most important feature of these esters is that they eliminate fat spew. They yield leather having a cleaner and more uniform surface, providing better anchorage for dyes, pigments and pigment finishes, and facilitating all finishing operations.

The present invention, therefore, not only opens up an entirely new field for the leather chemist in the development of new tanning, stun.- ing and fat-liquorlng agents, but also introduces into this field a class of substances having properties which have been well defined, classified and proven in the field of synthetic resins and varnishes. It is a further advantage of the invention that these materials are already available to the tanner and leather finisher in large quantities at a reasonable price, for their sources of supply have already been developed to an enormous extent in the wide field of resin, paint and varnish manufacture. Accordingly, the present invention accomplishes the result of carrying over into one art all the experience and development in another entirely unrelated and more recently developed art, with all the advantages attendant upon this transference.

As has been stated, the low vapor pressure esters of organic acids possess, in addition to their plasticizing action, the important property of lubricating the fibers of skins and leather to the same or greater extent than the stufling and fatliquoring agents now in use, and these substances are particularly valuable for this reason. However, as might be expected in such a large class, it has been found that the esters of certain organic acids have more desirable properties than do those of other acids, and that certain alcohols or other esterifying agents are also more useful than are others of the same class. For example, I have found that esters of the organic dicarboxylic and polycarboxylic acids are more desirable stufilng agents than are the esters of the monocarboxylic acids, and therefore form a preferred class of substances for use in practicing the invention. For obvious wmmercial reasons the action of the cheaper and more available organic diand polybasic acids have been more completely investigated than have the rarer and more expensive ones, and I have found that esters of phthallc,

. maleic, fumaric, succinic, tartaric, oxalic, citric,

sebacic and adlpic acids can all be used either singly or in admixture in the tanning, stuffing and fat-liquoring of leather. This statement, however, should not be taken to mean that esters of the monocarboxylic acids are without utility in practicing the invention, for I have found that esters of acids such as benzoic, benzoyl benzoic, stearlc, salicylic, abietic and the like are also of advantage. It is understood, of course, that the above acids specifically enumerated are merely representative of the classes to which they belong, all members of these classes being useful in practicing the invention, and that the corresponding substitution products and homologs of these acids such as the corresponding halogenation products. sulfonation products, nitro compounds, amido or amino or hydroxy compounds, etc. may be used in similar manner.

Another class of acids which are of importance in the preparation of lubricating and plasticizing esters for use in practicing the invention are those obtainable by the condensation of unsaturated acids with compounds containing a conjugated double bond system by the diene synthesis. Representative acids of this class are the hydroaromatic and terpenic mono-, diand polycarboxylic acids and their homologues obtained by the condensation of maleic acid and anhydride, acrylic acid and the like with unsaturated hydrocarbons such as butadienes, terpenes, cracked gasolines and the like, carboxylic acids such as abietic acid, and natural fats and oils and their modification products such as linseed oil, tung oil, castor oil and the fatty acids derived from these glycerides.

The alcohols or other esterifying agents which can be used in preparing the low vapor pressure esters which form the preferred stufiing and fatliquoring agents of the present invention may be selected from a wide range of compounds, as is known in the manufacture of plasticizers. Any monohydric alcohol of the paraffin series may be used, such as methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, as well as the corresponding higher alcohols of parafiinic or waxy nature such as cetyl alcohol, ceryl alcohol, lauryl alcohol, and even melissyl alcohol, which contains 30 carbon atoms. A particularly useful class of higher alcohols of this nature for use in the present invention is that derived from the reduction, with metallic sodium or otherwise, of the fatty acids obtained from vegetable and animal oils, these alcohols ranging from 12 to 18 carbon atoms and being characterized by the presence of an even number of carbon atoms. In addition to the straight chain alcohols of the above classes, isomeric or branched chain alcohols may be used, including the lower alcohols such as isopropyl alcohol, isobutyl alcohol, i sobutyl carbinol or other isoamyl alcohols, pinacolyl alcohol, tetramethylethyl or other isomeric hexyl alcohols and the like, as well as higher alcohols of this nature. Another class of alcohols of value in producing esters for use in leather treatment are the ether alcohols, such as the methoxy, ethoxy and butoxy ethanols, etc.

In addition to'the saturated monohydric alcohols, the corresponding alcohols of the olefine or more highly unsaturated series may be used. Allyl and crotonyl alcohols are typical lower alcohols of this type which may be employed, while the entire series of unsaturated higher alcohols obtainable by the reduction of the unsaturated fatty acids of vegetable oils and fats may be em- 15 ployed. Mixed alcohols from special sources may also be used, such as the mixture of isomeric amyi alcohols obtainable from the absorption in sulfuric acid and subsequent hydrolysis of easing head gas or other petroleum fractions, and sold as "pentasoP, mixed alcohols from similar treatment of other petroleum fractions, synthetic lower and higher alcohols from the catalytic reduction of carbon monoxide or dioxide or from the hydrogenation of coal and oils, etc.

Another important class of alcohols which may be used in preparing esters for leathertreatment are those of a cyclic nature such as the aromatic alcohols, including benzyl alcohol, the tolyl carbinols, the naphthyl carbinols, dialkyl benzyl alcohols and the like. Another special type of compounds falling within this classification are the lactides, which may be produced for example, by reduction of dibasic and polybasic acids having two carboxyl groups in ortho position such as phthallde, which is a reduction product of phthalic anhydride and corresponds to an inner ester of benzyl alcohol with a carboxylic acid group in ortho position. This compound is at thesame time an ester of benzyl alcohol and benzolc acid, and imparts to leather the plasticizing characteristics and lubricating qualities of esters of both of these compounds. Other lactides such as those obtainable by partial reduction of acids resulting from the diene synthesis may also be used, typical examples of such acids being the condensation products of maleic acid with rosin, terpenes, tung oil, dehydrated castor oil and the fatty acids of these oils. Corresponding ester products of such acids may also be used, as will be pointed out in greater detail in the following examples. Hydrogenation and substitution products of the above compounds may also be used such as the hydrogenated and substituted phthalides, these derivatives having physical properties which vary with the degree of hydrogenation and substitution, and ofier in themselves a wide field of choice for the purposes of the present invention.

In addition to the aromatic alcohols, alcohols of the hydroaromatic series may be used such as cyclohexanol, hydrogenated naphthyl carbinols and the like. Alcohols of the heterocyclic series may also be employed and particularly those containing a furane nucleus, such as the furfuryl alcohols and tetrahydrofurfuryl alcohols, since these products are readily obtainable in commercial quantities.

In addition to the monohydric alcohols, diand polyhydric alcohols can also be used in which all butone of the hydroxy groups have been esterfied or etheriiled or both, with monoor poly-carboxylic acids and particularly with acids derived from natural fats or waxes. Examples of mixed esters of this type are di-glyceryl-phthalate-tetraacetate, di-glyceryl-phthalate-tetra-oleate, and di (di-butoxy-glyceryl) phthalate.

Of course other alcohols and acids may also be used, for instance, monoor poly-hydroxy organic acids containing one or more carboxylic groups, in which, acids one or more of the hydroxy groups are either esterified, etherified or left free. In general the above classes represent those which are commercially available.

It is understood that any of the esters which may be prepared by esteriflcation of the above alcohols, either singly or in admixture, with acids of the classes above enumerated may be used in the tanning, stufllng and fat-liquoring of hides and leather. These esters are well suited for use as the sole treating agent in these processes, but

another improvement feature of the invention resides in their use in conjunction with the natural fats and oils which are now used for these purposes. This is important, not only by reason of the wider field of choice which is made available to the tanner by the use of a mixture of treating agents, but also because of the long experience which tanners have acquired with the natural oils and fats, which becomes available in applying the plasticizers of the present invention. When low vapor pressure plasticizers, and especially esters are used in conjunction with the natural oils and fats, their relative stability and the greater lubricating properties which many of them possess will result in improvements in existing stufling and fat liquoring processes and will result in leathers of fuller and softer characteristics. This field of application of the invention is, of course, a large one and the tanner will employ mixtures best suited to his own special needs.

It should be mentioned in this connection however that the esters of phthalic acid, and particularly ,the dimethyl, diethyl and di-butyl phthalates, possess the important characteristic of impermeability to the ultra violet light which hastens rancidity in natural oils and fats, and the incorporation of even small quantities of phthalic acid compounds in the stuffing and fatliquoring preparations now in use will result in an increased stability and longer life of the leather.

Another feature of the invention which is of greatpractical importance resides in the modification of the low vapor pressure esters by the introduction of inorganic or organic substituents. For example, the sulfonation of these esters, or the use of sulfonated acids or sulfonated alcohols in their preparation, results in increased emulsifying and penetrating properties, which are of great advantage in fat-liquoring, and the introduction of nitro, amino, halogen, hydroxy and similar groups also will impart special properties. The most important products of this nature are, of course, sulfonation products, as is shown by the fact that sulfonated natural oils are now in use in fat-liquors and wholly or partially sulfonated esters may be used to substitute or supplement these sulfonated oils with great success. A particularly useful method of applying this feature of the invention is the partial sulfonation of the completed esters, or the use of a mixture of sulfonated and unsulfonated acids in esterifying, whereby an incompletely sulfonated product is produced. This feature of the invention permits the preparation of fat-liquors having exactly the right emulsification and penetrating properties for hides and skins of varying characteristics, as well as for leathers which have been subjected to special tannages such as iron tannage, chrome tannage, aldehyde tannage, quinone tannage,

alum tannage, etc. It is well known that the pH of the leather and of the fat-liquoring bath has a profound effect upon the stability and penetration of fat-liquoring emulsions and the depth to which these emulsions will penetrate the leather before they break and deposit the lubricant upon the fibers of the hide, and the use of partial or progressive sulfonation or other pre-treatment of the esters of the present invention forms a ready means of controlling this stability and penetration.

Perhaps the most important field of applying plasticizers to leather in accordance with the present invention is in the fat-liquoring of leather, either bleached or unbleached. These leathers, for example, gloye leather, upper leather, calf skins, etc., are usually subjected to chrome taunage or to a light vegetable tannage and are frequently given an after bleach with naphthalene sulfonic acid derivatives or other bleaching agents, such as those described in my Patent No. 2,029,322 in order to give a lighter shade to the leather. After these treatments, the leather would dry stiff and hard, so it is drummed or otherwise treated in an emulsion of a relatively water insoluble fat-liquoring agent or agents to lubricate and soften the fiber. In this process the lubricating properties of the low vapor pressure esters are of great advantage, and their use in this process is a most important feature of the present invention. I have found, however, that it is occasionally necessary to add surface active agents to these low vapor pressure esters in order to produce the best emulsions for use in this process, and that this combination of ingredients will produce a fat-liquorlng emulsion having hitherto unsuspected properties. Accordingly, these mixtures of low vapor pressure esters with surface active agents, and the fat-liquoring emulsions prepared therefrom, I regard as new products of great utility, and these new products constitute another feature of the present invention.

A wide choice of surface active agents is available in preparing the stufflng and fat-liquoring mixtures constituting this feature of the invention, for almost any of the known classes of surface active agents may be successfully employed. Some of these surface active agents may be classifled roughly as follows:

(i) Sulfonated aromatic hydrocarbons and their homologs, such as sulfonated naphthalene, propyl or isopropyl, butyl or isobutyl and amyl naphthalene sulfonic acids, or their ammonium, alkali metal or triethanol amine salts.

(2) Salts of sulfonated aromatic or aliphatic esters of mono-, diand polycarboxylic acids such as the dipropyl, diamyl, dibutyl, di- (methyl amyl) or di-octyl esters of sulfonated phthalic acid.

(3) Sulfated or sulfonated higher alcohols, such as sulfonated lauryl or other alcohols prepared from the fatty acids of vegetable oils.

(4) Sulfonated mineral, vegetable or animal .oils such as the Aquasols" which are castor oils of varying degrees of sulfonation.

(5) Sulfonated amides and irnides of aromatic or aliphatic mono-, diand polycarboxylic acids.

(6) Salts of diene condensation products, such as the sodium, ammonium or triethanolamine salts of the condensation products of abietic and maleic or fumaric acids and their esters, salts and sulfonation products.

(7) Soaps of various fatty acids such as oleic, stearic, palmitic and those obtained from talloel or black liquor soap in wood pulp manufacture.

(8) Certain fatty acids and their monoor diglycerides such as wood soap fatty acids, glyceryl mono-ricinoleate, di-glycerol oleate, etc. Sulfonated fatty acids may also be used.

(9) Sulfonated terpenes and their condensation products such as pinene phenol sulfonate.

(l0) Salts of phosphoric acid esters of higher alcohols or of phosphoric compounds of higher hydrocarbons.

(ll) Salts of quaternary ammonium compounds such as the ester of lauric alcohol with chlorpyridino acetic acid.

Naturally, certain of the above surface active agents are more effective than are others for the emulsification of any-given low vapor pressure ester or mixture thereof, but all of the above classes of surface active agents will impart improved fat-liquoring properties to any of these esters in greater or lesser degree. In the follow-: ing specific examples I have pointed out representative esters and representative surface active agents which have been employed with good resuits, and these will serve to indicate to the tanner the way in which the most suitable stufiing and fat-liquoring compositions can be prepared for any particular leather which he may desire to finish. Insofar as the surface active agents containing sulfonic acid or sulfuric acid groups are concerned, which represent the most successful of the surface active agents which have been employed, it has been found that the products of a higher degree of sulionation such as the Aquasols, and other highly sulfonated vegetable oils and the like give better results when used in conjunction with low vapor pressure esters than do the less highly sulfonated products, and accordingly these form a preferred class of substances for use in conjunction with the present invention. However, the wide range of practical conditions dealt with in leather finishing, and the great number of types of leather involved make it dlfiicult to state anything other than the most general principles involved in the selection of the best surface active agents for use in con- Junction with the low vapor pressure esters for any given purpose, and the tanner will naturally select those which he finds most suitable to his own finishing process.

A further field of application of the invention lies in the filling or stufilng of sole leather or other heavy leathers of similar nature. In this process a mixture of mineral and/or animal and/or vegetable substances is introduced into the leather by drumming or similar processes, in order to give weight and substance thereto. Frequently animal, vegetable and mineral oils are used in this process to provide lubrication during the drumming of the leather and to prevent damage to the grain, as well as to provide additional lubrication to the leather fibers, and I have found that the esters and other plasticizers described above which have a lubricating action on the fiber of the leather are well suited for this pur- POse. Standard materials which have been used in the filling of sole leather are, for example, a mixture of cod oil, mineral oil and sulfonated oil together with filling materials such as sugar, Epsom salts and tanning extracts. Any or all of the above, oily materials, either sulfonated or unsulfonated, may be replaced in whole or in part by the esters and other compounds that have been described for use in the present invention, including those specifically referred to in the following examples. It is understood, therefore, that this step in the finishing of heavy leather is included in the present invention, and is intended to be covered by the appended claims.

In applying the above synthetic plasticizers and esters to the leather, and particularly during stuffing and fat-liquoring processes, it is sometimes desirable to alter or adjust their physical and/or chemical characteristics in accordance with the requirements of different leathers and different steps in the process. This can readily be done by bodying the synthetic compounds by the addition of natural or synthetic resins, gums and waxes insofar as they are compatible with the particular plasticizer or mixture of plasticizers selected. For example, the alkyl phthalates, and particularly diethyl, dipropyl and dibutyl phthalates, may be heated with unmodified or oil-modified alkyd resins in small amounts, whereby their viscosity is increased and they are converted into desirable filling and stuffing agents.

In' the application of the plasticizers and ester emulsions of the present invention to the oiling,

, stufiing and fat-liquoring of hides, skins and leather, any of the standard manipulative processes now in use may be employed. These processes are well described in the publication above referred to, and this description need not be repeated here. The most widely used method involves the introduction of the tanning, stuffing or fat-liquoring agents into the hides by agitation in a rotating drum, with or without the continuous or intermittent application of a vacuum thereto, and the present invention is well suited for use in conjunction with this method of application. In the following examples, the results obtained with representative compositions containing the plasticizers and solvent softeners of the present invention are given, the amounts of reagents given being based on the weight of the leather. It should be understood however that these examples are given merely by way of illustration of the principles of the invention and that the specific details thereof are illustrative only and do not constitute a limitation upon the invention in its broader aspects. It should also be noted that where, in these examples, a specific ester or mixture of esters is used in conjunction with a specific emulsifying agent, this is intended to illustrate the results obtainable with these classes of materials and that equivalent materials from the same or different classes may be substituted without departing from the scope of the invention. The invention in its broader aspects is to be limited only by the scope of the claims appended thereto. 7

While a number of the plasticizers and esters used in the treatment of hides and skins according to the present invention are excellent tanning agents for oil tannages, and particularly the esters of unsaturated acids and/or alcohols such as maleic acid esters, and while they are also useful in syntan tannages, I do not claim specifically these functions of these compounds as this part of the invention is claimed in my copending application Serial No. 95,032, filed Aug. 8, 1936.

Example 1 A water emulsion containing 2% of dihexyl phthalate, based on the weight of the leather, is prepared using 1% of an emulsifying agent such as Aquasol AR 90%, which is a highly sulfonated castor oil. This is readily done by agitating the ester for a few minutes and slowly adding a water solution containing the emulsifying agent with continuous stirring.

Chrome tanned calfskins are well washed and sometimes bleached for one hour, using a bleaching agent such as Tanak C. They are then fat-liquored in the above emulsion by agitating in a drum for one hour at 60 C., using 60% of their weight of water and 3% of the lubricating material. The leather is then rinsed in water, set out and dried.

Upon examination it is found that the finished leather is soft and flexiblewith a smooth, satiny feel on the grain side, but without greasiness. The fat-liquoring bath exhausts well which shows that substantially all the plasticizer is taken up by the leather.

Additional emulsions were prepared using varyins ratios of surface active agent to ester. in. order to determine their relative effect on the leather. The following table shows the results obtained.

Ratio: Surface Percent on active agent weight of g g to cater leather LAquasol AR 90% 3 Fair. 2. Do 1 Poor.

3. {Ackuasol AR 90% l Di exyl phthslate 2 Good. 4. Dihexyl phthalate.- 0. 75 Good. 2. 25 Good. 5. Dihaxyl hmmaun 0. e0 2. 40 Good. 6. A uasol AR 90% 0.45 Di exyl phthalate.. 2. 55 Good. 7. {Dihexyl phthalate--.-- 0. 36 2. 64 Good.

Good lubrication was obtained in all cases where the ester was used. with complete absorption of the lubricant, which shows that the ratio of ester to emulsifying agent may be varied through a wide range.

Example 2 Chrome tanned calfskins were fat-liquored in emulsions prepared as in Example 1, using 2% of dibutyl phthalate, dioctyl phthalate and dilauryl phthalate, respectively, together with 1% of Aquasol AR 90% as emulsifying agent. Good absorption of the lubricating materials was obtained and no surface deposition was noted. The

lubrication was good, and soft pliable leathers In order to determine the relative value of various surface active and emulsifying agents, standardized water emulsions of these substances were prepared with dibutyl phthalate, using the procedure outlined in Example 1. 1% of the emulsifier and 3% of the ester were used.

Calfskins were fat-liquored with these emulsions in the usual manner. The results obtained were as follows:

Lubrication Emulsilying agent Emulsion 0 leather Very stable Good. Glyoery ricmolea .-do Do. Black liiluor fatty acid soaps -.-do Do. Di-glyco oleate Siable.--.-- Do. leopr'oayl naphthalene sodium sul- --.do Do. ona Wood soap fatty acids --do Do. Twitchell Oil 4X do Do. Bulfonawd vegetable oil ..do Do. Di-octyl sodium suliosuoeinato --d0 Do.

Emulsions containing emulsion stabilizers such as gum tragacanth, colloidal clay and the like together with emulsifying agents such as pinene phenol sulfonate were also prepared, using 3% of dibutyl phthalate and 1% each of the emulsifying agent and emulsion stabiliser. Very stable emulsions were obtained which gave good lubrication to the leather.

From the above it is apparent that-any emulsifyins agent capable of producing a sufllciently stable emulsion of ester in water is suitable for use in fat-liquoring when used with or without the addition of an emulsion stabiliser.

mple 4 A fat-liquoring emulsion is prepared containing 6% of a sulfonated neats-foot oil, together with 1% of dioctyl phthalate. Glove leather is agitated in this'emulsion for one hour and is then washed, dried, and tested for pliability. A

. may be substituted, wholly or partially, for the dioctyl phthalate.

trample 5 Esters of maleic acid are emulsified with water as in Example 1, using, for example, 1% of a highly sulfonated oil such as Aquasol AR 90% as emulsifying agent. Emulsions containing 84% of the following esters were prepared and tested for fat-liquoring and lubricating proper ties:

Di-amyl maleate Di-amyl fumarate Fumarate of du Pont alcohols H'I'P-B 23 Fumarate of du Pont alcohols HI'P-B 24 Dioctyl fumarate Di-(sec.)tetradecyl fumarate Di-carbitol maleate Di-capryl fumarate Well lubricated samples of leather were obtained in all cases.

It will be noted that all the above fat-liquorlng agents are simple di-esters of monohydric alcohols,. and for the most part primary and secondary alcohols. These simple compounds appear to have excellent lubricating properties and form the subject matter of the more specific claims of the present application. The application to hides, skins and leather of more complex compounds, in which the distinguishing radical is a polyhydric alcohol or a natural oil or fat in which for one or more of the fatty acid radicals of the natural glyceride the radical of one of the non-fatty monoor poly-carboxylic acids is substituted, is not specifically claimed in the present application but forms a part of the subject matter of my copending application Serial No. 95,032 filed August 8, 1936.

Example 6 Vegetable tanned leather is fat-liquored in an emulsion containing 5% of amyl benzoyl benzoate and 1% of Aquasol AR 90%, based on the weight of the leather. Good lubrication is obtained, and the bath after the leather is removed shows good exhaustion.

Instead of amyl benzoyl benzoate, butyl chlorobenzoyl benzoate may be used with equally good results.

Example 7 Four parts of di-hexyl succinate and one part of di-hexyl sulfosuccinate sodium salt are emulsiiled in water as in Example 1 and 100 parts of leather are treated in this bath for hour in a revolving drum. A well lubricated leather results, having none of the greasy feel that sometimes is experienced when vegetable or animal oils are used for this purpose.

Instead of the di-hexyl ester, other esters of succinic acid may be used, such as di-octyl succinate, dibutoxy ethyl succlnate, etc.

Example 8 Instead of using simple esters from a single alcohol, as in some of the preceding examples, mixed esters containing two or more alcohols combined with a single organic acid may be used for the stuiling and fat-liquoring of leather. Similarly, a mixture of chemically distinct esters may be used, as follows:

A mixture containing 75% of di-amyl fumarate and 25% of di-octyl fumarate is prepared. 2-5 parts of this mixture are emulsified in water, using 1-2 parts of di-octyl sodium sulfosuccinate as emulsifying agent. Light chrome and vegetable tanned leathers fat-liquored in these emulsions show lubrication equal to and in some cases better than those treated with the best sulfonated oils now in use, with good exhaustion of the emulsion.

The following table shows the results obtained from tests using these materials:

Additional tests were run using ratios up to 19: 1 of ester to emulsifying agent. It was found at .the higher ratios that only fair lubrication was obtained, but that this was improved as soon as sufllcient of the emulsifying agent was present to insure a good water dispersion of the ester.

Example 9 Heavy, vegetable tanned leathers such as sole leather, belting leather, harness leather and the like are stuffed or filled with oils, with or without other filling materials such as sucrose, magnesium sulfate, sulfite cellulose and the like, in order to add fullness and flexibility thereto.

For example, wet sole leather is placed in a rotatable drum provided with a liquid inlet and outlet in the axis thereof. A charge of diethyl or dibutyl phthalate is added and the drum is rotated until 3-5% of the ester has been absorbed into the fibers of the leather. The leather after washing and drying is well lubricated and shows excellent resistance to ultraviolet light.

Instead of esters which are normally liquid, viscous or solid esters may be used and may be rubbed into the leather as in hand stuffing. Sodium salts of the half esters of phthalic acid with alcohols such as lauryl alcohol, octyl alcohol and methyl amyl alcohol are well suited for this purpose, being soft, waxy solids having natural lubricating properties at ordinary temperatures. Other esters which may be used in this manner, preferably after warming to increase fluidity if necessary or in admixture with esters of sulfonated acids such as di-octyl or di-(methyl amyl) sodium sulfosuccinate, dihexyl sodium sulfophthalate and 'the like, are di-cyclohexyl phthalate, ethoxy ethyl bsnzoyl benzoate, di-methyl maleate, di-methyl fumarate and the like. Glycol and glyceryl derivatives of organic dibasic acids also have excellent lubricating properties and being heavy, viscous liquids at ordinary temperatures are well suited for use in hand stufllng and finishing compositions of the above type. Representative compounds of this class are glycol succinate, diethylene glycol succinate, diethylene glycol fumarate, di-glyceryl maieate, di-methyl-diethylene glycol di-fumarate and dibutyl glycol di-phthalate, which may be used alone or in admixture with each other or with impregnating agents such as sulfonated oils, esters of sulfonated dicarboxylic acids, alkyl naphthalene sulfonic acids and the like. However, I do not claim specifically in this application the use of esters of polyhydric alcohols with polybasic acids for leather treatment since this forms apart of the subject matter of my copending application above referred to.

In addition to their suitability for hand stufling the esters of the present invention, and particularly those of the higher alcohols with polybasic acids, are also well suited for drum stufling and filling of heavy leathers in admixture with many of the unsulfonated and sulfonated vegetable oils, fish oils and'animal oils now used for this purpose.

Example 10 7 Charges applied in the above manner were:

1. 8 parts sugar 5.5 parts sodium octyl phthalate The sodium octyl phthalate, and the corn sugar were heated with stirring until the mixture was homogeneous.

2. 5 parts mineral oil, cocoanut oil or fish oil 2 parts di-methyl fumarate 8 parts corn sugar A part Turkey red oil Prepared as in 1. All these materials were well taken up by the leather; the cut was goodand the feel satisfactory.

Example 11 A special class of polybasic acids which may be esterified with monohydric or polyhydric alcohols for the preparation of plasticizing esters for use in the lubrication and preservation of leather in accordance with the invention are those derived from the diene synthesis. These acids are 7 --c=o-co with a compound which contains or develops during the reaction one or more systems of conjugated double bonds of. the type By heating together or otherwise reacting these components in the absence or presence of condensing agents or inert materials such as solvents, cyclic acids of a hydroaromatic nature are obtained which upon further. treatment form plasticizers which are well suited for leather finishing.

Among the unsaturated acids and acid-forming materials which may be condensed in this manner maleic acid and anhydride, fumaric acid and acrylic acid are perhaps the most important commercially, but other acids of this nature may also be used. For example itaconic acid, citraconic acid and crotonic acid and unsaturated acids of the aralkyl type such as cinnamic acid may be employed. In general any unsaturated mono or polycarboxylic acid containing the above mentioned grouping may be used, either in the pure state or in admixture with other substances.

A wide range of compounds containing the diene or conjugated double bond linkiage are known and can be used for condensation with unsaturated acids of the above character, and this class includes compounds such as terpenes which develop such linkages during the reaction. When simple hydrocarbons such as butadiene or hydrocarbon fractions containing this substance or other hydrocarbons containing one or more conjugated systems of double bonds, for example, cracked gasoline, are condensed with maleic or fumaric acid a product containing a tetrahydrophthalic acid nucleus is obtained which, when reacted with monohydric or polyhydric alcohols or their mixtures, is well suited for use in accordance with the invention. Similarly, hydrocarbons such as cyclopentadiene, cyclohexadiene, phellandrene, myrcene, isoprene, dimethyl butadiene, phenyl butadiene, methyl phenyl butadiene and the like may be reacted with any of the above mentioned unsaturated acids to yield derivatives of phthalic, benzoic and other cyclic acids which form esters having excellent properties for the lubrication of leather. Other hydrocarbons which are readily obtainable and are well suited for use are the acetylene polymers produced by the absorption of acetylene in ammoniacal cuprous chloride solution such as the acetylene tetramer 1,5,7 Octatriene-3-ine, and coumarone and indene obtained from coal tar distillates, all of which can be condensed with maleic, fumaric, or other similar unsaturated acids to yield acids suitable for use in the form of their esters as above described.

In addition to the hydrocarbons, other unsaturated compounds may be condensed with unsaturated acids of the above described type, for example heterocyclic compounds such as pyrrol, methyl pyrrol, furanes, furfural thiophenes and ths like. Pine oil, sulfate turpentine and other compounds of similar nature may be used. A special class are the terpenes containing carboxylic acid groups and also containing or forming conjugated double bond systems such as abietic acid which, when condensed with maleic, fumaric .and similar acids yield triand polycarboxylic acids. Any of the above substances may be reacted with the unsaturated acids which have been described to produce acids which can be partially or completely reacted with monoor polyhydric alcohols, glycols, monoor diglycer-' ides and the like to produce excellent stuiilng, filling and fat-liquoring agents for hides, skins and leather in accordance with the invention.

a A class of compounds which are particularly well-suited for use in the lubrication of leather are the esters of acids obtainable by the condensation of maleic, fumaric or other unsaturated acids of the above described class with the natural oils and the products obtainable therefrom. Many of these oils, such as tung oil, linseed oil and the like, are the glycerides of fatty acids which contain or develop conjugated double bond systems and such. oils, or the fatty acids obtained therefrom, may be directly condensed with the unsaturated acids by simple heating to temperatures of 150-200 C. Other oils, such as castor oil and perilla oil, can be modified by dehydration into products containing such double bond systems. Still other oils, such as fish oil, teaseed oil, neats-foot' oil, mineral oils and the like must be subjected to more extensive treatment to convert them into products capable of reacting with unsaturated acids by the diene synthesis, as by halogenation and subsequent dehalogenation, treatment with permanganate solutions and subsequent dehydration, etc. In all cases. however, the resulting cyclic acid derivatives when esterifled show greatly improved qualities of stability and resistance to spewing and rancidity in comparison with the original oils from which they were prepared, and are well suited for the purposes of the present invention.

As an example of the above, tetrahydro-ophthalic acid obtained by the condensation of equimolecular quantities of maleic acid and butadiene is esterified with butyl or amyl alcohol and an emulsion containing 2% of the product and 1% of an emulsifying agent such as Aquasol AR 90%, based on the weight of the leather, is used for the fat-liquoring of chrome tanned calfskins as in Example l.- Leather of equally good characteristics is obtained, and the fat-liquoring bath exhausts well.

Instead of tetrahydro-o-phthalic acid, the endomethylene 3,6(delta 4) cis-tetrahydrophthalic acid obtained by the diene condensation of cyclohexadiene with maleic acid may be used with equally good results.

As an example of natural oils, .tung oil is mixed with maleicanhydrlde in equimolecular proportions and the mixture is heated to 180 C. The resulting condensation product after esterification with methyl alcohol is mixed with Aquasol AR 90%, using a ratio of ester to Aquasol of 5:1, and 6% of the mixture is used in the form of an emulsion to fat-liquor bleached and unbleached chrome leather in the following manner:-

Chrome tanned calfskins are washed in running water and treated with the fat-liquoring emulsion, some with preliminary bleaching at 50 C. for one hour with Tanak A and others in the unbleached state. The fat-liquoring was continued for one hour at 60 C. with an emulsion containing 60% water and the lubricating materials. After fat-liquoring the leather was rinsed in warm water, set out, dried and examined for degree of lubrication and color. Leather iat-liquored with the original untreated oils was also prepared by corresponding treatment and was compared with the condensation products for light resistance.

Similar fat-liquors were prepared using the following esters and chrome tanned calf leather was lubricated according to the above described procedure:

Tung oil maleic anhydride condensation product. ethyl ester Tung oil fumaric acid condensation product,

methyl and dimethyl ester Dehydrated castor oil maleic anhydride condensation product, methyl ester Linseed oil maleic anhydride condensation product, methyl ester.

In all cases a satisfactory degree of lubrication of the leather was obtained and the color of the leather was good. Good exhaustion of the fatliquoring baths was.obtained.

Representative samples of each of the above leathers were tested for resistance to ultraviolet light in comparison with corresponding samples fat-liquored with the untreated oils by exposure to light from a sun lamp for several hours. In all cases the pieces fat-liquored with esters of the condensation products showed less discoloration than those fat-liquored with the natural oils.

What I claim is:

1. The method of fat-liquoring, filling or stuffing hides, skins and leather which comprises introducing into the same a low vapor pressure ester of an organic carboxylic acid selected from the group consisting of aromatic acids, hydroaromatic acids and polybasic aliphatic acids.

2. The method of fat-liquoring, filling or stuffing hides, skins and leather which comprises introducing into the same a low vapor pressure ester of an aromatic dicarboxylic acid.

3. The method of fat-liquoring, filling or stuffing hides, skins and leather which comprises introducing into the same an ester of phthalic acid.

4. The method of fat-liquoring, filling or stuffing hides, skins and leather which comprises introducing into the same a low vapor pressure ester of an aliphatic polybasic carboxylic acid with a monohydric alcohol.

5. The method of fat-liquoring, filling or stuffing hides, skins and leathers which comprises introducing into the same a low vapor pressure ester of an aliphatic polybasic acid selected from the group consisting of maleic acid, its isomer fumaric acid, and its reduction product succinic acid.

6. The method of fat-liquoring, filling or stufling hides, skins and leather which comprises introducing into the same a low vapor pressure ester of a monohydric alcohol with an organic acid selected from the group consisting of sulfonated organic dicarbcxylic acids and the alkali metal, ammonium and amine salts thereof.

7. The method of fat-liquoring, filling or stufilng hides, skins and leather which comprises introducing into the same a low vapor pressure ester of an organic carboxylic acid selected from the group consisting of aromatic acids, hydroaromatic acids and polybasic aliphatic acids and a surface active agent.

8. The method of fat-liquoring, filling or stuffing hides, skins and leather which comprises introducing into the same a low vapor pressure ester of an organic carboxylic acid selected from the group consisting of aromatic acids, hydroaromatic acids and polybasic aliphatic acids and an ester of a sulfonated organic acid.

9. A method of fat-liquoring hides, skins and leather which comprises contacting them with an aqueous emulsion containing a low vapor pressure 7 ester of an organic carboxylicacid selected from the group consisting of aromatic acids, hydroaromatic acids and polybasic aliphatic acids.

10. A method of fat-liquoring, filling or stufling hides, skins and leather which comprises introducing into the same a mixture of low vapor pressure esters of one or more organic carboxylic acids at least one of which is selected from the group consisting of aromatic acids, hydroaromatic acids and polybasic aliphatic acids.

11. A method of fat-liquoring, filling or stufiing hides, skins and leather which comprises introducing into the same a mixture containing a low vapor pressure ester of an organic carboxylic acid selected from the group consisting of aromatic acids, hydroaromatic acids and polybasic aliphatic acids and a natural oil or fat.

12. A method of fat-liquoring, filling or stufling hides, skins and leather which comprises introducing into the same an ester of a phthalic acid with a monohydric alcohol.

13. The method of fat-liquoring, filling or stuffing hides, skins and leather which comprises introducing dimethyl phthalate thereinto.

14. The method of fat-liquorlng, filling or stufling hides, skins and leather which comprises introducing into the same an ester of an organic acid which is a dime condensation product of an unsaturated organic acid containing the group and an organic compound containing a system of conjugated double bonds.

15. The method of fat-liquoring, filling or stufi'ing hides, skins and leather which comprises introducing into the same an ester of an organic acid of the hydroaromatic series which is a diene condensation product of an unsaturated organic acid selected from the group consisting of maleic acid and its isomer fumaric acid and an organic compound containing a system of conjugated double bonds.

16. The method of fat-'liquoring, filling or stufling hides, skins and leather which comprises introducing into the same an ester of an organic acid of the hydroaromatic series which is a diene condensation product of an unsaturated organic acid selected from the group consisting of maleic acid and its isomer fumaric acid and an unmodified or modified oil containing a system of conjugated double bonds.

17. The method of fat-liquorlng, filling or stuffing hides, skins and leather which comprises introducing into the same an ester of an organic acid of the hydroaromatic series which is a diene condensation product of an unsaturated organic acid selected fromthe group consisting.

of maleic acid and its isomer fumaric acid and an unmodified or modified vegetable oil containing a system of conjugated double bonds.

18. The method of fat-liquoring, filling or 'stufling hides, skins and leather which comprises introducing into the same an ester of an organic acid of the hydroaromatic series which is a diene condensation product of an unsaturated organic acid selected from the group consisting oi maleic acid and its isomer fumaric acid and the fatty acid of an unmodified or modified vegetable 011 containing a system of conjugated double bonds.

19. The method of fat-liquoring, filling or stufiing hides, skins and leather which comprises introducing into the same a monohydric alcohol ester of an organic acid of the hydroaromatic series which is a diene condensation product of an organic acid selected from the group consisting of maleic acid and its isomer fumaric acid and an unmodified or modified vegetable oil containing a system of conjugated double bonds.

20. A fat-liquoring, filling or stufiing composition for hides, skins and leather comprising a normally liquid, low vapor pressure ester of an organic carboxylic acid selected from the group consisting of aromatic acids, hydroaromatic acids and polybasic aliphatic acids and a surface active agent.

21. A fat-liquoring, filling or stufiing composition for hides, skins and leather comprising'a normally liquid, low vapor pressure ester of an organic dicarboxylic acid and a surface active agent.

22. A fat-liquoring, filling or stufling composition for hides, skins and leather comprising a normally liquid, low vapor pressure ester of a phthalic acid and a surface active agent.

23. A fat-liquoring, filling or stuffing composition for hides, skins, and leather comprising a water emulsion of a low vapor pressure ester of an organic dicarboxylic acid.

24. A fat-liquoring, filling or stufling composition for hides, skins and leathercomprising a water emulsion of a low vapor pressure ester of a phthalic acid.

25. A fat-liquoring, filling or stuffing composition for hides, skins and leather comprising a water emulsion of a low vapor pressure ester of a polybasic aliphatic carboxylic acid.

26. A fat-liquoring, filling or stuffing composition for hides, skins and leather comprising a water emulsion of a low vapor pressure ester of an aliphatic polybasic acid selected from the group consisting of maleic acid, its isomer fumaric acid, and its reduction product succinic acid.

2'7. A fat-liquoring, filling or stuffing composition for hides, skins and leather comprising an aqueous emulsion of a dialkyl phthalate.

28. Hides, skins and. leather lubricated with a low vapor pressure ester of an organic carboxylic acid selected from the group consisting of arcmatic acids, hydroaromatic acids and polybasic aliphatic acids.

29. Hides, skins and leather lubricated with a low vapor pressure ester of an aromatic carboxylic acid with a monohydric alcohol.

30. Hides, skins and leather containing as a lubricant an ester of phthalic acid.

31. Hides, skins and leather containing as a lubricant a low vapor pressure ester of an aliphatic polybasic acid selected from the group con sisting of maleic acid, its isomer fumaric acid, and its reduction product succinic acid.

ALPHONS O. JAEGER. 

